This invention relates to the use of a synthetic Asialo GM1 (T-beta) antigen to elicit production of monoclonal antibodies which bind to tumor cells.
T-alpha antigen, also known as the TF (Thomsen-Friedenreich) antigen, is the immediate precursor of the human blood group MN antigens. Tn, in turn, is the immediate precursor of the T-alpha antigens. Normally, T-alpha antigens are not accessible to the human immune system because they are masked by sialosyl groups. Friedenreich exposed the T-alpha antigen by treatment of red blood cells with neuraminidase, whereupon they were bound by anti-T components of human sera.
Kim and Ohlenbruck determined that the immunodominant portion of the T antigen was the disaccharide beta-D-Gal-(1-3)-alpha-D-GalNac. Z. Immun-Forsch. 130:88-89 (1966). It was later established that in contrast to healthy tissues, certain adenocarcinomas presented T-alpha and Tn determinants in reactive, unmasked form. Springer, et al., Cancer, 45:2949-54 (1980).
This T-alpha determinant has been prepared synthetically. Ratcliffe, et al., Carbohydr. Res., 93:35-41 (1981); Lemieux, EP Patent 44,188 (publ. May 28, 1986). Example 11 in the latter reference describes the use of T-alpha hapten on an HSA carrier (at incorporations of 7, 12, 14 and 22 haptens per HSA molecule) to detect a delayed type hypersensitivity response. The use of such haptens in the production of anti-T-alpha monoclonal antibodies was not mentioned. A synthetic T-alpha hapten is also described by Kolar, U.S. Pat. No. 4,442,284.
Rahman and Longenecker, J. Immunol., 129:2021-2024 (1982) used the natural form of the T-alpha antigen (neuraminidase-treated erythrocytes) for the production of monoclonal antibodies whose binding to these cells was competitively inhibited by synthetic T-alpha hapten. Thus, their use of synthetic T-alpha hapten was as a characterizing agent.
Asialo-GM1, a gangliotetraosyl ceramide with the structure Gal (beta 1-3) GalNac (beta 1-4) Gal (beta 1-4) Glc (beta 1-1) ceramide, is found in brain tissue in its sialated form. The immunodominant portion of this molecule (the terminal disaccharide), shown in boldface, differs from that of TF by the substitution of a beta linkage (underlined) for an alpha linkage, and hence is referred to herein as T-beta (as distinct from T-alpha). Lemieux, U.S. Pat. No. 4,137,401 discloses reaction conditions for linking a bridging arm to an aldose by a beta-D-anomeric glycosidic linkage. Synthetic T-beta haptens have been used in a number of immunological studies. Hoppner, et al., Vox-Sang., 48:246-53 (1985); Rahman and Longenecker, supra; Longenecker, et al., Int. J. Cancer, 33:123-129 (1984). However, use of synthetic T-beta haptens in production (as opposed to characterization) of monoclonal antibodies is novel.
Kasai purified the asialo GM1 glycosphingolipid and used it to prepare polyclonal anti-asialo GM1 antibodies. Eur. J. Immunol., 10:174-80 (1980).
The terminal disaccharide of asialo GM1 is of interest because it, like T-alpha, appears to be a tumor-associated antigen. Habu, et al., J. Immunol., 125:2284-88 (1980); Nakahara, et al., New Eng. J. Meal. 302:674-677 (1980). Hakomori tried and failed to make a monoclonal antibody to asialo GM1. Hakomori, in Monoclonal Antibodies and Functional Cell Lines: Progress and Applications, 67-100 (1984).
Goldenberg, U.S. Pat. No. 4,444,744 generically describes the use of radiolabeled antibodies to tumor cell surface antigens for diagnostic purposes. He teaches broadly that antibodies may be labeled by radiohalogen substitution or by chelation to a radiometal such as Indium-111. As one in a long litany of tumor cell surface antigens, he mentions T antigen. We have not seen any reports of radioimaging work on T-like structures in any of Dr. Goldenberg's work. Metal chelate-conjugated monoclonal antibodies are disclosed by Gansow, U.S. Pat. No. 4,454,106 and U.S. Pat. No. 4,572,509. On immunotherapy and immunoimaging see generally Monoclonal Antibodies: Potential Applications to the Treatment of Cancer, Seminars in Oncology, 13(2):165-179 (June, 1986).
Other references of interest are Irie, U.S. Pat. No. 4,557,931 and Adachi, U.S. Pat. No. 4.389,392.